While shadow masks have been manufactured and used for deposition of materials in industry for an extended period of time applications for the pealable deposition masks used in active matrix organic light emitting devices (OLED) require greater precision and accuracy than previous manufacturing applications required.
A process used to manufacture a pealable deposition mask forms a pealable deposition mask onto a plate. The pealable deposition mask is a electroformed on the plate using a metallic compound, which is then chemically etched using a patterned photo-resist. The pealable deposition mask is then manually removed from the plate. The process of removal includes pealing the pealable deposition mask from the plate by first lifting a corner and drawing the electroformed material way from the plate. The process is as consistent as the manual process can be performed person to person. The pealable deposition masks are thin maliable material making them susceptible to deformation. The pealable deposition mask after removal has structural deformation and curl due to the directional draw of the peeling process. The pealable deposition mask is also affected by inconsistent peeling direction and the any change in the angle the pealable deposition mask is peeled away from the plate.
The pealable deposition mask must be now mounted to a frame used in the deposition process. The pealable deposition mask is presently mounted to the frame manually using a alignment device (commonly-assigned U.S. Pat. No. 6,475,287 B1). The pealable deposition mask must first be manually aligned to the frame. Next, the pealable deposition mask is held as planer as possible using an alignment plate. The alignment plate attempts to hold the already curled and structurally deformed pealable deposition mask as flat as possible while the process of manually applying adhesive strips to the outer edge of the pealable deposition mask and the deposition frame simultaneously, attaching the pealable deposition mask to the frame. When individual adhesive strips are applied directional stresses are introduced into the pealable deposition mask. The directional stresses cause rippling or waves in the mounted pealable deposition mask. The rippling is detrimental to the deposition process. The pealable deposition mask must be as co-planer as possible to the substrate during the deposition process for accurate deposition of materials.
In making organic light emitting devices (OLED) there are a number of steps in which organic layers are deposited on or over a substrate. It is essential that pealable deposition mask be aligned and properly mounted so that accurate deposition takes place. The pealable deposition mask is typically a precision mask made of a thin malleable material. The pealable deposition mask is lithographically patterned and because it is thin it permits the appropriate location of organic material to be deposited on or over the substrate. The pealable deposition mask has to be properly mounted and the aligned to the substrate. The following is a description of a standard technique used to mount and align the pealable deposition mask. The prior art typically uses a frame and manually centers the mask relative to the frame. Tape is often used to secure the pealable deposition mask to the frame. The frame with the mounted pealable deposition mask is positioned in a vacuum chamber relative to the substrate.